The present invention pertains to novel, discrete, crosslinked vinylidene chloride polymer microgels which are particularly effective as additives for synthetic foams and fibers and for the preparation of improved coatings, films and redispersible latexes.
Microgel polymer structures are known in the art. For example, U.S. Pat. No. 3,285,887 discloses discrete, cross-linked polymers prepared by the emulsion polymerization of a mixture of a bifunctional crosslinking agent with an ethylenically unsaturated monomer selected from the class consisting of olefinic hydrocarbons, olefinic ethers, amides and esters. Such materials are described as being particularly useful as thickeners for lubricating oils.
Further, reactive microgels prepared by the emulsion polymerization of functional monomers, such as 1,4-divinylbenzene or various alkylene glycol-dimethacrylates are described in J. Oil Col. Chem. Assoc. 1977, 60, 438-445 by W. Funke. These materials are described as being useful as multifunctional crosslinkers for reinforcing purposes and as reactive components in condensation and addition polymerization reactions.
Reactive microgels prepared from divinylbenzene are also disclosed in the following articles:
Obrecht, Seitz, Funke, Makromol. Chem. 175, 3587 (1974). PA0 Obrecht, Seitz and Funke, Makromol. Chem. 176, 2771 (1975). PA0 Obrecht et al., Makromol. Chem. 177, 1877 (1976). PA0 Orbecht et al., Makromol. Chem. 177, 2235 (1976). PA0 Seitz et al., Makromol. Chem. 178, 1689 (1977).
Crosslinked polymers of vinyl halides, including copolymers of vinyl chloride and vinylidene chloride, are also known in the art. For example, U.S. Pat. No. 4,022,849 discloses crosslinked vinyl halide polymers for use as flame-retardant additives for thermoplastic materials.
It is an object of the present invention, however, to provide certain vinylidene chloride polymer microgels having unexpected applicability as flame-retardants and physical property enhancers for synthetic materials, such as polyurethane foams and acrylic fibers, and for the preparation of coatings, films, and latexes having improved characteristics.
More specifically, it is an object of this invention to provide vinylidene chloride polymer microgels which are dispersible in nonsolvents for vinylidene chloride polymers, such as polyols which are conventionally used to prepare urethane foams and elastomers, and which will further provide enhanced strength and flame-retardance to such materials.
It is another object to provide vinylidene chloride polymer microgels which can be easily introduced in synthetic fibers, such as acrylic fibers, to impart increased flame-retardance thereto with only moderate loss in fiber processability or strength properties.
It is yet another object to provide vinylidene chloride polymer microgels which provide redispersible latexes.
It is a still further object to provide vinylidene chloride polymer microgel latexes which can be tailored to provide amorphous coatings having high vinylidene chloride content or crystalline coatings having greater flexibility.
It is another object to provide vinylidene chloride polymer microgels which may be used to provide lacquer coatings for substrates such as cellophane and other plastic films, such coatings providing improved heat seal temperatures and flexibility.